From Sea Dart to Sea Viper – area air defence for the Royal Navy

In this article, we consider the highly regarded Sea Viper missile carried by the Royal Navy’s Type 45 destroyers and its predecessor, the Sea Dart missile system.

2G SAM

The Sea Dart GWS-30 surface to air missile system began development in 1960s and first went to sea with HMS Bristol in 1973. This was the RN’s second-generation area air defence missile and replaced the cumbersome Sea Slug carried by the County class destroyers which was virtually obsolete even before it entered service. The Sea Dart was originally designed to counter medium and high altitude Soviet aircraft and was initially ineffective against sea-skimming targets due to limitations of the sensor and guidance technology carried by the ship. During the 1982 Falklands War its performance was mixed, 26 Sea Darts were launched in anger, achieving 8 confirmed kills. To date, Sea Dart retains a unique place in history as the only missile to take out another missile in action. During the first Gulf War in February 1991, HMS Gloucester destroyed a land-launched Iraqi Silkworm missile heading for USS Missouri.


The Sea Dart was a two-stage ramjet missile manufactured by British Aerospace from 1970. On launch, the solid fuel booster burned for 2.5 seconds propelling the missile up to about Mach 2.5 before falling away. A kerosene-powered Rolls Royce Odin ramjet motor would take speed up to about Mach 3.5 and burn for the entire flight, providing good manoeuvrability at extreme range. The later version of the missile had a theoretical range of about 150km, although very much subject to the limitations of the ship’s radar. The target was initially acquired by the Type 1022 long-range air search radar. Once launched, it was guided by its semi-active homing system which relied on the ship illuminating the target with one of its two dedicated Type 909 fire-control radars. Four antennae on the nose of the missile picked up the reflected signals using an analogue interferometer to calculate the homing trajectory. This method of guidance was susceptible to jamming, although resistance improved with the later versions.

  • HMS Edinburgh conducts the last ever Sea Dart firing, 13 April 2012. The Type 909 Fire Control Radars are under the prominent GRP radomes fore and aft. The large Type 1022 air search radar is mounted on the forward stub mast.

  • A Type 42 destroyer with 2 red-painted dummy rounds on the twin launcher (live rounds are white).

  • Sea Dart away – in an eruption of flame and smoke, the missile accelerates to Mach 2.5 in the time it took to read this sentence. Note the lowered guardrails and the hose playing cooling water onto the deck.

  • The foredeck of HMS Cardiff after firing missiles in combat during the Falklands War. One of the many advantages of vertical launch missiles is a lot less soot covering the upper deck!

  • Type 42 destroyer Sea Dart magazine where the missiles were stowed vertically in cradles. The cradles were moved around on a shock-mounted rail system and positioned on hydraulic rams which lifted them up onto the launcher.

  • HMS Manchester receives Sea Dart via Replenishment At Sea, April 1988. The bulky missile canister is transferred horizontally from the RFA stores ship via jackstay. It is then attached to a hydraulic arm on the launcher and raised to the vertical position. The missile is then withdrawn from the bottom of the canister by another hydraulic ram that lowers it down to the magazine below. The empty canister is returned to the RFA. (Photos: Kev Slade)

  • Misfire during a test-launch from HMS Gloucester. The disintegration of the booster was probably due to the age of the rocket motor and was caused by a failure of the bonding between the propellant and insulation. The main missile fell harmlessly into the sea while the booster burned itself out, causing minor damage to the upper deck.

  • Sea Dart Missile

    An early iteration of the Sea Dart showing the Odin ramjet core surrounded by Kerosene fuel tanks.

Sea Dart weighed 550kg and carried an 11kg warhead, being reasonably compact, it had an overall length including booster of 4.4m. Besides the prototype Sea Dart launcher fitted to HMS Bristol, the system was also fitted to the 14 RN Type 42 destroyers (commissioned between 1975-85) and the 3 CVS aircraft carriers. The system failed to attract any export orders except the unfortunate sale to Argentina of two Sea-Dart equipped Type 42s. (UK-built ARA Hercules commissioned 1976 and locally built ARA Santísima Trinidad, commissioned 1981). Detailed knowledge of Sea Dart capabilities helped the Argentines mitigate some of its effectiveness during the Falklands conflict. The subsequent suspension of after-sales and technical support quickly made the system inoperable by the Argentine Navy in the years following the conflict. Sea Dart was removed from the CVS in the late 1990s in favour of more flight deck space and the magazine converted to store aircraft ordnance.

Despite its successes in combat, the initial Mod 0 Sea Dart System had a very mixed record of reliability and misfires. The launcher was originally designed to placed on the aft end of a ship (as in HMS Bristol) but when sited on the short and more exposed foredeck of the Type 42s, suffered badly from to seawater ingress. The launcher problems were eventually solved and there were many other planned upgrades. A more radical development known as Sea Dart Mark 2 (GWS 31) was cancelled in 1981 Defence Review but incremental improvements were made over its lifetime. The most significant development came with the Mod 2 (1989) version which focused on the radars and guidance software. This almost doubled the range, enabled more than two targets to be engaged simultaneously, improve clutter discrimination, allowed re-targeting during flight and the ability to fire on crossing targets.

By the early 1990s, the system had matured to a point where had become reliable and accurate but was far behind the US Navy’s VLS-based AEGIS system and could not effectively defend against saturation attacks. Rate of fire was limited to about two missiles every 30 seconds, far behind the capability of modern vertical launch cells. The Batch 1 and 2 Type 42s could only embark an outfit of up to 24 missiles but the four ‘stretched’ Batch 3 vessels had their magazine capacity expanded to 42. Approximately 2,000 Sea Dart rounds were manufactured in total over its 40-year lifetime.

Sea Dart finally went out of RN service in 2012 as the now obsolete missiles could no longer be economically maintained beyond that date. Delays to the introduction of the replacement Type 45 destroyers saw HMS York and Edinburgh continue to serve for another year, despite no longer carrying their main armament. The Sea Viper that replaced the Sea Dart was a vast improvement but the older system did have the advantage that rounds could be replenished at sea and had a limited anti-ship capability.

The mighty Viper

  • A rare photo of an Aster 30 in its lifting cradle. Costing around £2 Million each, they are expensive but relatively good value for such a sophisticated weapon. Several thousand Aster (in several variants) have now been manufactured for nine nations keeping unit cost down.

  • Aster 15 about to be inserted in its storage canister. Note the much smaller first stage booster compared with the Aster 30.

  • The twin nozzles of the first-stage booster made by Avio in Italy. Avio also manufactures the propellant, igniter, motor case, fins, and Thrust Vector Control (TVC). Avio also manufactures the sustainer motor of the terminal dart.

  • An Aster 30 missile canister is loaded onto HMS Diamond at the UHAF in Portsmouth. The size of the canister underlines why it would be almost impossible to perform this operation safely at sea. MBDA says it normally takes about 90 minutes to reload each of the six 8-cell VLS modules. If no one took a break this means it would take 9 hours for a Type 45 to load a full outfit of missiles.

  • The Longbow barge carrying a complete replica of the PAAMS(S) towed out of Portsmouth on her way to the south of France for trials, July 2007.

  • Final checks at MBDA factory. Each missile is a piece of precision engineering that must withstand enormous forces.

Sea Viper is the RN’s name for Principal Anti-Air Missile System/Sampson (PAAMS)(S) which consists of several interdependent parts. The Sampson radar, the S1850M radar, the command and control system, the Sylver Vertical Launching System and Aster 15 or Aster 30 missiles. (This article is primarily about the Aster missiles and we will focus on the equally important radars in a future piece.)


Unlike the all-British Sea Dart, Sea Viper is the product of multi-national European co-operation. It might be considered the silver lining of the otherwise the disastrous UK-French-Italian Horizon project which attempted to develop a Common New Generation Frigate (CNGF). Divergent national requirements saw the UK withdraw from the frigate project in 1999 and design its own (6) Type 45 destroyers. The French and Italians persevered but eventually managed to build just 2 Horizon frigates each. These 10 ships are all equipped with PAAMS, although the Type 45s are much superior in the area air defence role, mounting the more capable Sampson radar.

Development of Aster dates back to 1989 when France and Italy began joint development of a missile that could be used for both land and naval air defence. The first Aster was test-fired in December 1994 and was successfully developed over a number of years, achieving the first operational firing (of an Aster 15) from the French carrier Charles de Gaulle in October 2002. In November 2003, EUROSAM (A joint venture between what is now MBDA and Thales) was awarded a €3 Billion contract by the European Defense Procurement Agency (OCCAR) to manufacture 1,400 Aster 15 and 30s for naval use and for French & Italian SAMP/T ground-based systems.

Work on the development of PAAMS began in August 1999, with the Aster missile already maturing, there was high confidence the project would be successful. Aster is manufactured in France and Italy but Sea Viper has a significant industrial footprint in the UK including MBDA’s integration facility in Bristol, the MoD’s Eskmeals facility in Cumbria, BAE Systems’ Cowes Radar Integration Test Facility and the Maritime Integration & Support Centre (MISC) at Portsmouth.

The first PAAMS(S) missile trial for the RN took place at the Centre d’Essais de Lancement des Missiles (CELM) test range off the French Mediterranean coast on 4th June 2008 from the trials barge ‘Longbow’. A Mirach target flying at about 32,000 ft was destroyed at 35km range. PAAMS(S) was officially renamed Sea Viper by the RN in January 2009. The Longbow barge built in Portsmouth carried a complete replica of the Type 45 destroyer PAMMS fit and a more demanding test, successfully engaging a low-level anti-ship missile at close range was made 4 February 2009. Manufacturing faults with Aster missile led to two failures during high G manoeuvring tests in late 2009 and delayed the in-service date by 10 months. The first Type 45, HMS Daring commissioned in July 2009 unable to fire its primary armament and it was the second ship, HMS Dauntless that made the first test-firing of Sea Viper in September 2010.


Aster-30-Sea-Viper-Missile-1

There are two variants of the missile used by the Royal Navy. The short/medium range Aster 15 provides point and local area defence against low level and hard manoeuvring aerial targets. The official effective range is about 30Km, very slightly superior to the Sea Ceptor, although its minimum engagement range is 1.7km. Aster 15 can reach Mach 3 and weighs just 310kg, considerably lighter than the similar size 550kg Sea Dart.

Aster 30 is the big brother and of greater importance to the Type 45’s area air defence mission to create a defensive bubble over the Carrier Strike Group, Littoral Strike Group or shipping convoys. Aster 30 can reach targets up to 120km away from the launch point and at an altitude of 20 km. Travelling at up to Mach 4.5 (5,380 kph), technically Aster 30 is not quite fast enough to be described a Hypersonic itself but when combined with the Sampson radar, both Aster 15 and 30 are capable of intercepting inbound hypersonic missiles.

Both weapons are propelled by a two-stage rocket. The first-stage booster designed and produced by Avio is considered one of the most powerful and technologically advanced solid-propellant motors available. The second stage ‘Terminal Dart’ is identical for both variants, the Aster 30 having a much larger first-stage booster which provides its extra range and speed.

Lethal

What makes Aster especially potent is its manoeuvrability derived from its PIF-PAF system. PAF (Pilotage Aeronautique en Force) uses long chord wings and fins for strong aerodynamic control authority. This is supplemented by PIF (Pilotage Intertiel en Force) consisting of four gas jets acting through the centre of gravity of the missile. The narrow jets are integrated into the fins to avoid disruption of the airflow and are capable of generating rapid lateral movements to keep the missile on target. There are other missiles that use thrust vectoring but what may be unique is the use of the central PIF jets to apply a force to the body in the opposite direction to manoeuvre-induced G-force to prevent the missile rupturing under stress. Engineered to cope with trajectory corrections up to 60G, there is certainly no aircraft and probably no missile that could out-manoeuvre a locked-on Aster in its terminal phase.

Which such a high level of accuracy it is thought that Aster can mitigate for the smaller number of VLS cells carried by European warships compared to the more numerous US Navy equivalents. Routine USN practice would be to fire a salvo of two or more Standard missiles at each target.

  • Aster 30 in flight.

  • HMS Defender successfully destroyed a ‘fast and low’ target during live-fire integrated air and missile defence (IAMD) Exercise Formidable shield, May 2019.

  • HMS Duncan 2014. Since 2010, all six of the RN’s Type 45s have successfully destroyed Mirach drone targets during serials held at the Benbecula ranges in the Outer Hebrides.

  • The Type 45 destroyers are fitted with six 8-tonne SYLVER (SYstème de Lancement VERtical) A50 packs. Each pack contains 8 cells (providing a total of 48) and can take missiles up to 5 meters in length. The missile hatches are watertight and are designed to protect the missiles from shrapnel in RATTAM (Response to ATTack on AMmunition)-proof casing. The centreline uptakes hatches open to vent the rocket motor efflux. (HMS Daring, 2012.)

The Missiles are launched automatically on command from the combat management system on a course derived from the target’s initial detection and classification by the Sampson radar. During the first part of the flight, the Aster is guided by its own Inertial Navigation System (INS), until mid-course updates are sent from the ship via data uplink. To reduce warning time, in the final seconds of the terminal phase, the missile becomes autonomous and locks onto the target using its active 12-18Ghz (J-band) pulse-doppler AD4A radar seeker. Aster does not have an infrared homing system found on some comparable missiles as a back up terminal guidance method. However, the seeker has its own electronic counter-countermeasures (ECCM) capabilities that include home-on-jam and clutter suppression.

The 15kg Avio/MBDA directional blast fragmentation warhead is fitted with a Ku-band proximity fuse and has two types of fragments; small 4 gram and larger fragments, which are expelled in the direction of the target.

The precise capabilities of Sea Viper are obviously classified but it is known to be highly automated with rapid response times specifically designed to cope with saturation attack. MDBA say that at least eight missiles can be fired within about 10 seconds and 16 missiles guided to targets concurrently. Actual performance may be even better but it is too expensive and complex to test these scenarios for real, confidence is derived from live test data combined with sophisticated simulations.

The RN still utilises the Aster 30 Block 0 but France and Italy have continued to develop its capabilities into 3 other variants. Block 1 is Part of the Italian/French SAMP/T land-based air defence system and is modified to defend against ballistic and conventional missiles. Block 1NT (New Technology) can intercept tactical and short-range ballistic missiles. As covered in previous articles, the UK remains ‘interested’ in Ballistic Missile Defence but has yet to commit to spending money on hardware. The Type 45 could be upgraded for BMD and embark either Aster 1NT or be fitted with Mk41 cells and utilise the US-made SM-3 missile. For now, curing the propulsion issues and returning all 6 ships to the active fleet has to be the priority.

Summary

Although the Type 45 destroyers have suffered a rocky journey into service, overshadowed by cuts to planned numbers, cost over-runs and propulsion issues, their Sea Viper system is the one of the RN’s ‘crown jewels’. The combination of the British-developed Sampson radar and the Franco-Italian Aster missile is formidable and rightly regarded as the best naval air defence system at sea today. There are many elements of the Sea Viper system that are essentially ‘black boxes’, the workings of which are only fully understood by a small number of technical experts. Its true effectiveness could only be judged in a real shooting war that no one wants. It was notable that when HMS Duncan was buzzed by 17 Russian jets in the Black Sea during 2018, the TV documentary recorded the senior officer on board saying: “their tactics are naive, what they don’t know is how capable this ship is”. It is not hard to imagine Sea Viper dispatching multiple waves of aircraft at the push of a button.